1. Field of the Invention
Embodiments of the invention relate to semiconductor devices, and more particularly, to semiconductor devices including antifuses.
2. Description of the Related Art
An antifuse has a high resistance in its initial state. An antifuse can permanently create an electrically conductive path when a relatively high voltage is applied across the antifuse. An antifuse can have a structure similar to that of a capacitor, i.e., two conductive electrical terminals are separated by a dielectric layer. To create an electrically conductive path, a relatively high voltage is applied across the terminals, breaking down the interposed dielectric layer and forming a conductive link between the antifuse terminals. Creating a conductive path through an antifuse is referred to as “blowing an antifuse.”
Antifuses are often used in memory cell arrays such as dynamic random access memories (DRAMs). For example, after testing a DRAM, failed cells in the DRAM can be repaired by remapping. An antifuse typically stores the remapping.
FIG. 1 illustrates a conventional parallel antifuse system 100. The illustrated system includes decoders 101-104 and antifuses 111-114. Each of the antifuses 111-114 has a unique address associated with it. The decoders 101-104 are configured to receive and decode signals from a controller (not shown) to blow selected antifuses 111-114. The illustrated system 100 uses a parallel scheme to access the antifuses 111-114 in that each of the antifuses 111-114 are individually and separately accessed using their unique addresses.
As the number of antifuses in a device increases, this parallel scheme can be slow to program and wasteful of chip area. The parallel scheme uses a relatively large logic circuit to decode the addresses of the antifuses. In addition, complex routing may be required to provide access to the antifuses. For example, in a memory device (e.g., DRAM) having large numbers of rows and columns in its memory array, the parallel scheme can substantially complicate the design of the device.
In addition, it is often desirable to detect whether antifuses have been fully blown to determine whether a desired electrical path has been created. In one arrangement, a fixed blowing time is given for each antifuse. Such a fixed blowing time can be redundant or insufficient depending on the antifuses being blown. If it is redundant, it can result in a waste of time and current resources to blow antifuses. On the other hand, if it is insufficient, a desired electrical path may not be established.